Surface mountable circulator/isolator and assembly technique

Abstract

A structure for a passive microwave device capable of low IMD and high power operation, and adapted for automated assembling and placement is disclosed. The device exhibits a high degree of coplanarity on its mounting surface, as well as a high degree of flatness and alignment between its respective components. The inherent self-aligning qualities of the design are used in conjunction with an assembly fixture that has three or more alignment pins to provide a highly manufacturable and reliable device. Related manufacturing methods and fixturing are also disclosed.

1. A passive microwave device, comprising:
 a printed circuit board having a plurality of conductive ports, a ground portion, and at least three aligning holes that are configured to receive alignment pins of an assembly fixture;  
 a housing secured on the ground portion of the printed circuit board, and including a bottom portion having three or more centering slots, each centering slot corresponding to one of the aligning holes of the printed circuit board; and  
 a stack including a center conductor that is configured with three or more aligning portions that are each adapted to couple with a corresponding alignment pin of an assembly fixture.  
 
   
   
     2. The device of  claim 1  further comprising:
 a pressing cover disposed on top of the stack, and configured to tightly fit into an inner perimeter of the housing.  
 
   
   
     3. The device of  claim 2  further comprising:
 a locking cover disposed on the pressing cover, and configured with a number of teeth spaced on its periphery, wherein the locking cover is rotated so that the teeth engage flare slots defined in the housing thereby locking the stack in place.  
 
   
   
     4. The device of  claim 1  wherein the printed circuit board has a stack side and a host side, and further includes a plurality of metallized via holes that electrically and thermally couple the stack side to the host side. 
   
   
     5. The device of  claim 1  wherein the conductive ports and ground portion of the printed circuit board each have a stack side and a host side, each conductive port having a metallized pad on its host side that is substantially coplanar with the ground portion of the host side. 
   
   
     6. The device of  claim 1  wherein the center conductor further includes a plurality of tuning stub resonators in symmetrical relation to one another, and each aligning portion is disposed on an end of a respective tuning stub resonator. 
   
   
     7. The device of  claim 1  wherein each aligning portion of the stack is disposed on the stack's periphery and is configured with a surface adapted to couple with a corresponding alignment pin of an assembly fixture. 
   
   
     8. The device of  claim 1  wherein the center conductor further includes a plurality of transformer arms in symmetrical relation to one another, each arm having an end portion that is electrically and mechanically connected to a respective conductive port on the printed circuit board. 
   
   
     9. The device of  claim 1  wherein the stack further includes at least one of a ground plane, a magnet, a ferrite, a pole piece, and a temperature compensator, with each stack element having one of at least three alignment holes configured to receive alignment pins of an assembly fixture, or a common shape that allows minimal play when the element is placed between alignment pins of an assembly fixture. 
   
   
     10. The device of  claim 1  wherein the stack further includes a ferrite element on at least one side of the center conductor, the center conductor further including tuning stub resonators and transformer arms in symmetrical relation to one another, with each tuning stub resonator extended to an edge of the one or more ferrite elements in a radial direction. 
   
   
     11. The device of  claim 1  wherein the center conductor further includes tuning stub resonators and transformer arms in symmetrical relation to one another, with each tuning stub resonator extended toward its neighboring transformer arms in an azimuthal direction. 
   
   
     12. The device of  claim 1  wherein the bottom portion of the housing further includes a number of relief openings, each relief opening coinciding with a respective conductive port location on the printed circuit board. 
   
   
     13. The device of  claim 1  wherein the housing is made from a single piece of sheet metal. 
   
   
     14. An assembly fixture for manufacturing circulator/isolator devices, the fixture comprising:
 a body; and  
 three alignment pins extending vertically from a top surface of the body, two of the pins having a fixed position, and the third pin having an adjustable position, wherein the pins are adapted for at least one of: 
 coupling with corresponding holes and slots of elements included in a circulator/isolator device being assembled; and  
 limiting radial movement of circulator/isolator device components disposed between the alignment pins.  
 
 
   
   
     15. The fixture of  claim 14  wherein the length of the pins is slightly less than the device's height so as to allow a cover to rest on the assembly without contacting the pins. 
   
   
     16. A method for manufacturing a circulator/isolator device, the method comprising:
 placing a printed circuit board on an assembly fixture having three or more alignment pins, the printed circuit board having at least three aligning holes that are configured to receive the alignment pins of the assembly fixture;  
 placing a housing on a central ground portion of the printed circuit board, the housing including a bottom portion having three or more centering slots, each centering slot corresponding to one of the alignment pins of the assembly fixture; and  
 placing a stack in the housing between the alignment pins of the assembly fixture, the stack including a center conductor that is configured with three or more aligning portions that are each adapted to couple with a corresponding alignment pin of the assembly fixture.  
 
   
   
     17. The method of  claim 16  wherein the method produces a circulator/isolator device, the method further comprising:
 placing the circulator/isolator device on a host system thereby contacting coplanar conductive ports and a ground portion of the printed circuit board with corresponding contacts of the host system.  
 
   
   
     18. The method of  claim 16 , wherein the center conductor further includes a plurality of transformer arms in symmetrical relation to one another, the method further comprising:
 electrically and mechanically connecting an end portion of each transformer arm to a respective conductive port on the printed circuit board.  
 
   
   
     19. The method of  claim 16  wherein the center conductor further includes a plurality of transformer arms and tuning stub resonators in symmetrical relation to one another, the method further comprising the preliminary step of:
 forming the center conductor so that its tuning stub resonators extend toward its neighboring transformer arms in the azimuthal direction, and extend to an edge of ferrite elements included in the stack.  
 
   
   
     20. The method of  claim 16  further comprising:
 disposing a pressing cover on top of the stack, the pressing cover configured to tightly fit into an inner perimeter of the housing.  
 
   
   
     21. The method of  claim 20  further comprising:
 disposing a locking cover on the pressing cover, the locking cover configured with a number of teeth spaced on its periphery;  
 rotating the locking cover so that the teeth engage flare slots defined in the housing thereby locking the stack in place; and  
 securing the locking cover with a bonding material.